Resolving the Concerns of Aging

    As life expectancy perpetually increases throughout the developed world, the proportion of the aged population increases simultaneously. Although most of us likely do desire the extra years of life, we certainly do not want the downsides that tag along with it, such as a decreases of physical stamina and mental strength, as well as the more superficial concerns of simply looking "old" (how many botox procedures were there last year?).

    We fear far more, however, having to helplessly watch our mental capabilities disappear, as occurs in diseases such as Alzheimer's and Parkinson's. Our neurons begin to degenerate in these diseases, and our aged human brains lack the regenerative capacities to restore them. This is because we no longer possess the stem cells that were present near the beginnings of our lives: only infants and young children possess such regenerative capacity and plasticity. The human brain begins to "weed out" unnecessary neurons and change gene expression as it ages in order to, at least in part, increase its efficiency for specific capabilities that are used in everyday life. In doing so, it loses its ability to heal itself, thus leaving it defenseless when neurodegenerative diseases attack. There is currently a limited number of treatment options available, though none even remotely resembles a cure.

    Research in this area has exponentially increased in the past decade, with scientists taking many different approaches. One is to copy nature's solution, the very one used by our younger selves: stem cells. Stem cell therapies for these diseases have been found to demonstrate both neuroregenerative capacities, as well as inhibition of the inflammatory cytokine response by our own immune system, which normally exacerbates neural degeneration. However, one of our greatest fears of these treatments is the application of these cells to humans because (1) it is unknown how well our aged, established neural networks can handle neuronal replacement, and (2) administration of stem cells is extremely invasive, holding high potential for injury.

    I had the opportunity to hear Dr. Jessica Brann explain how she and her colleague, Dr. Stuart Firestein, were examining the first issue at Loyola's Neuroscience Seminar series. They study the epithelial lining of the vomeronasal organ (VNO), which is one of the few areas in the nervous system that contains cells "capable of lifelong proliferation." First, the team studied the neuroregenerative capacity of VNO stem cells in aged mice, as opposed to previous studies that had examined these cells purely in young mice. Analysis of cell proliferation throughout the lifespan of aged mice showed that these cells continue replacing neurons just as quickly as young mice. Second, and perhaps more interestingly, they found that the ability of these stem cells to respond to injury also remained intact in aged mice. Thus, the VNO contains stem cells that are capable of generating functional neurons both "throughout life and in the aged animal." This discovery is significant because it shows that the nervous system can handle the replacement of neurons even in its aged and established networks of neurons, thus providing hope for the success of neuronal replacement therapies in humans. On the other hand, a team of scientists in Germany is studying the latter problem of stem cell application, but they are doing so in a very novel manner: by applying stem cells to rats with a Parkinson's-like disease via stem cell inhalation. As absurd as this may sound, they had overwhelming success. The stem cells did not spread to unintended areas of the body, as has occurred in surgical and intravenous methods. Furthermore, the cells demonstrated regenerative abilities, reduced cytokine inflammation responses, and prevented apoptosis of neural cells. Apparently, the technique is even easy to apply.

    Although neither of the two teams have yet examined human application, their results bring us one step closer to the creation of a truly viable treatment by helping to resolve some of the concerns of treatment application. Development of neuronal regeneration therapies would not only make our lengthened life expectancies appear truly worthwhile, but we would finally be able to focus our time and energy on the more important issue: maintaining the appearance of a 25 year old indefinitely, but without frozen muscles.



 References

1. Lecture by Jessica Brann, Loyola Neuroscience Seminar. November 19th, 2013.

2. http://www.cellmedicine.com/inhaling-stem-cells-for-treating-parkinsons/